Natural circulation liquid pumping system in plume pumping system for test engines

ABSTRACT

A natural circulation pumping system, used in a plume pumping system for a test engine, having a liquid coolant in a reservoirseparator which supplies the liquid to a plurality of insulated downcomer tubes. The downcomer tubes are connected at their lower ends to an annular manifold. The liquid is returned to the reservoir-separator through a plurality of riser tubes wherein the vaporizing of the liquid, by the heat added, causes the liquid to circulate, since the liquid-vapor mixture in the riser tubes has less weight than the liquid in the downcomer tubes. Natural separation takes place in the reservoir-separator as the heavier liquid falls into the liquid pool and the light gas rises to be vented.

United States Patent Triplett 1 51 Sept. 26, 1972 [54] NATURAL CIRCULATION LIQUID Primary Examiner-Jerry W. Myracle PUMPING SYSTEM IN PLUME Attorney-Harry A. Herbert, Jr. et a1. PUMPING SYSTEM FOR TEST ENGINES 57 ABSTRACT [72] Inventor: Milton J. Triplett, Tullahoma, Tenn. A natural circulation pumping system, used in a plume [73] Assignee: The United States of Ameri a a pumping system for a test engine, having a liquid coorepresented by h secretary f the lant in a reservoir-separator which supplies the liquid Ai Force to a plurality of insulated downcomer tubes. The downcomer tubes are connected at their lower ends to [22] Wed: 1971 an annular manifold. The liquid is returned to the [211 APPL 7 40 reservoir-separator through a plurality of riser tubes wherein the vaporizing of the liquid, by the heat added, causes the liquid to circulate, since the liquid- [52] US. Cl ..73/ll7.l, 73/432 SD vapor mixture in the riser tubes has less weight than [51] Int. Cl. ..G0lm 15/00 the liquid in the downcomer tubes. Natural separation [58] Field of Search..73/l 16, 117.1, 432 SD; 62/100, takes place in the reservoir-separator as the heavier 62/101, 109, 141, 476 liquid falls into the liquid pool and the light gas rises to be vented.

[56] References Cited UNITED STATES PATENTS 5 Claims, 3 Drawing Figures 3,199,343 8/1965 Chi1ds et a1 ..73/117.1

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MM To 1/. TIE/Pl 77 QZM WJMW NATURAL CIRCULATION LIQUID PUMPING SYSTEM IN PLUME PUMPING SYSTEM FOR TEST ENGINES vacuum. conditions of space, pumps of a very large capacity are required. One of the most successful means of achieving this capacity is to freeze the exhaust gases on cryogenically cooled plates. However, as rocket engine sizes and engine run times have been increased, the required size of cryogenic refrigeration systems to cool these plates has become prohibitive. Two other methods have been used to obtain the cooling required: (I) circulating a pressurized and subcooled liquid cryogen through the passages in the pumping panels utilizing the specific heat, or (2) allowing the liquid in the panels to boil, utilizing the heat of vaporization. Both methods have difficult problems. Circulation pumps are expensive and the high pressures are not desirable when hazardous cryogens are used. Supply and distribution are difficult in the usual boiling system. Not all passages receive adequate cooling because of the difficulty of predicting and controlling two-phase flow. Even with adequate cooling, the system is frequently inefficient because of liquid entrainement in the exhaust gas.

BRIEF SUMMARY OF THE INVENTION According to this invention, use is made of the natural circulation caused by the difference in the force of gravity between a liquid and a liquid-vapor mixture. A reservoir-separator is located within a chamber and is positioned above a manifold at a lower elevation. The cryogenic liquid from the reservoir is supplied to a plurality of insulated downcomer tubes connected between the reservoir-separator and the lower manifold. A plurality of finned riser tubes are also connected between the reservoir and the lower manifold. Boiling occurs as heat is absorbed by the cryogenic liquid in the riser tubes. Since the weight of the liquidvapor mixture in the riser tubes is less than the weight of the liquid in the insulated downcomer tubes, circulation occurs. Also pumping of the liquid is automatically controlled by the amount of heat absorbed by the cryogenic liquid in the riser tubes.

IN THE DRAWING FIG. 1 is a schematic diagram showing a natural circulation cryogenic liquid pumping system according to the invention.

FIG. 2 shows a rocket engine test system using the cryogenic liquid pumping system of the invention.

FIG. 3 shows finned cryopumping surfaces used with the device of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION Reference is now made to FIG. 1 of the drawing, which shows a cryogenic liquid circulation system having a reservoir-separator 12. The cryogenic liquid from the reservoir 12 passes through a downcomer tube 14, covered with insulation 15, to a lower manifold 16 and then to uninsulated riser tube 18. The end of riser tube 18 extends into the reservoir separator 12. As heat is added to the cryogenic liquid in the riser tube 18 it is vaporized, thus using the heat of vaporization for cooling. The weight of the liquid-vapor mixture in riser tube 18, being less than the weights of the liquid in the downcomer tube 14, causes circulation to occur. This system also provides a natural reservoir-separator location. The liquid-vapor mixture leaving the end of riser tube 18 above the liquid level in the reservoir allows the liquid to fall out and return to the reservoir pool. The gases, being lighter, rise to the top of the reservoir for venting through vent tube 21. The reservoir level can'be maintained during operation by supplying cryogenic liquid from an external supply connected to supply tube 22 of the reservoir 12.

One system, with which the device thus far described may be used, is shown in FIG. 2. In this device, a plume pumping system 30 has a test engine 32 supported on a reaction block 34, in the conventional manner, with fuel supplied to the engine from fuel console 36 and oxidizer supplied from oxidizer console 38. Conventional radiation measuring apparatus 39, mass spectrometer probe 40, and plume pressure mapping device 41 are mounted on a conventional instrument support and traversing mechanism 42.

Conventional liquid nitrogen cooled liners 44, 45 and 46 act as a radiation shield and cool background for radiation instrumentation and to condense some of the water vapor from the test engine.

A liquid hydrogen cryopump 50 has an annular reservoir-separator 52 with a plurality of insulated downcomer tubes 54, only three of which are shown to simplify the drawing, an annular manifold 56 and a plurality of riser tubes 58 according to the invention. Liquid hydrogen is supplied to the reservoir-separator 52 through tube 60 from a supply, not shown. The reservoir-separator 52 is vented through a tube 62 which may lead to a hydrogen recovery system, not shown.

The liquid hydrogen cryopump condenses the bulk of the rocket engine gas and absorbs the main head load. Hydrogen is the only gas that does not condense on this pump.

To condense the hydrogen gas, a liquid helium cryopump 65 is provided. The liquid helium cryopump has a reservoir-separator 67, a plurality of insulated downcomer tubes 69, an annular manifold 71 and a plurality of riser tubes 73 which return to the reservoirseparator 67, as shown in FIG. 1. Liquid helium is supplied to the reservoir-separator 67, through tube 75 from a liquid helium dewar 77. The vented gas is fed to a recovery system, not shown, through tube 79.

To reduce the heat load on the liquid helium cryopump 65, the vented gas is supplied to gaseous helium cooled shield through tube 82 and is returned to vent tube 79 through tube 84.

The riser tubes 58 and 73 have cryopumping finned surfaces 86, as shown on tubes 73 in FIG. 3.

The operation of the liquid hydrogen and liquid heliurn cryopumps is as described with respect to FIG. 1.

While both liquid hydrogen and a liquid helium system have been described, the liquid hydrogen system alone could be used where there is no need to remove hydrogen gas; or, the liquid helium system could be used alone where only hydrogen gas is present. Also other coolant, such as liquid nitrogen, could be used, for example, where only water vapor and CO need be removed.

There is thus provided a natural circulation cryopump system for use in a test engine plume pumping system, which automatically increases and decreases the pumping action as the heat load changes.

- Iclaim:

1. In a system for testing an apparatus which produces a condensable gas within a chamber; including means for supporting an apparatus for test within the chamber; a cryopump system positioned within the chamber above the test apparatus, comprising: a liquid coolant cryopump within said chamber; said liquid coolant cryopump having a reservoir separator containing a liquid coolant; an annular manifold positioned beneath the reservoir-separator; a plurality of insulated downcomer tubes connected between the reservoirseparator and the annular manifold; a plurality of riser tubes connected to the annular manifold and extending into the reservoir-separator to a position above the surface level of the liquid coolant within the reservoirseparator, means for supplying a liquid coolant to the reservoir-separator to maintain the coolant at a predetermined level and means connected to the reservoir separator for venting the gas produced in the riser tubes.

2. The device as recited in claim 1 wherein the liquid coolant is hydrogen.

3. The device as recited in claim 1 wherein the liquid coolant is helium.

4. The device as recited in claim 3 for use in a plume pumping system for a test engine having means for supporting an engine for testing within the chamber; a test instrument support and traversing mechanism within the chamber; engine plume test apparatus supported on the instrument support and traversing mechanism; means for providing a cold background for the engine test apparatus; and including a second liquid coolant cryopump within said chamber; said second liquid cryopump containing liquid hydrogen and having an annular reservoir-separator surrounding the first reservoir-separator; an annular manifold positioned beneath the reservoir-separator; a plurality of insulated downcomer tubes connected between the reservoirseparator and the annular manifold; a plurality of riser tubes connected to the annular manifold and extending into the annular reservoir-separator above the surface level of the liquid hydrogen within the reservoir-separator, means for supplying liquid hydrogen to the annular reservoir-separator to maintain the coolant at a predetermined level and means connected to the annular reservoir-separator for venting the gas produced in the riser tubes.

5. The device as recited in claim 4 including a shield surrounding the riser tubes in the liquid helium cryopump; means for passing the gas vented from the liquid helium reservoir-separator through said shield.

* a a: a s 

1. In a system for testing an apparatus which produces a condensable gas within a chamber; including means for supporting an apparatus for test within the chamber; a cryopump system positioned within the chamber above the test apparatus, comprising: a liquid coolant cryopump within said chamber; said liquiD coolant cryopump having a reservoir separator containing a liquid coolant; an annular manifold positioned beneath the reservoir-separator; a plurality of insulated downcomer tubes connected between the reservoir-separator and the annular manifold; a plurality of riser tubes connected to the annular manifold and extending into the reservoir-separator to a position above the surface level of the liquid coolant within the reservoir-separator, means for supplying a liquid coolant to the reservoir-separator to maintain the coolant at a predetermined level and means connected to the reservoir separator for venting the gas produced in the riser tubes.
 2. The device as recited in claim 1 wherein the liquid coolant is hydrogen.
 3. The device as recited in claim 1 wherein the liquid coolant is helium.
 4. The device as recited in claim 3 for use in a plume pumping system for a test engine having means for supporting an engine for testing within the chamber; a test instrument support and traversing mechanism within the chamber; engine plume test apparatus supported on the instrument support and traversing mechanism; means for providing a cold background for the engine test apparatus; and including a second liquid coolant cryopump within said chamber; said second liquid cryopump containing liquid hydrogen and having an annular reservoir-separator surrounding the first reservoir-separator; an annular manifold positioned beneath the reservoir-separator; a plurality of insulated downcomer tubes connected between the reservoir-separator and the annular manifold; a plurality of riser tubes connected to the annular manifold and extending into the annular reservoir-separator above the surface level of the liquid hydrogen within the reservoir-separator, means for supplying liquid hydrogen to the annular reservoir-separator to maintain the coolant at a predetermined level and means connected to the annular reservoir-separator for venting the gas produced in the riser tubes.
 5. The device as recited in claim 4 including a shield surrounding the riser tubes in the liquid helium cryopump; means for passing the gas vented from the liquid helium reservoir-separator through said shield. 